控灌中蓄及减量施肥对稻田氮素动态的影响

为寻求高效生态的水-肥管理模式以减轻稻田施肥所引起的面源污染,在浙江省余姚试验区采用对比试验观测田面水与各土层土壤水中氮素形态及其质量浓度,对不同水肥管理模式下稻田氮素的变化规律进行分析。结果表明:施基肥7 d后减量施肥,田面水的NH+4-N质量浓度均值为常规施肥的46.14%,NO-3-N质量浓度均值为常规施肥的83.62%;控灌中蓄节水灌溉模式与减量施肥耦合能延长田间水的滞蓄时间,使稻田氮素肥料快速入渗并较多地保留在作物耕层,提高氮肥的有效利用率,降低田面排水的氮素浓度,减少氮素的深层渗漏;施肥后4 d内田面水的氮素浓度较高,应控制排水以避免氮肥流失,减轻稻田氮肥施用所引起的农业面源污染。

Effects of controlled and mid-gathering irrigation and reducing fertilization on dynamics of nitrogen in paddy fields

In order to establish an effective ecological management mode of irrigation and fertilization to reduce non-point source pollution caused by fertilization in paddy fields, nitrogen forms and mass concentrations in surface water and soil water in different soil layers were observed with comparative field trials in an experimental zone in Yuyao City of Zhejiang Province. The variations of nitrogen forms in paddy fields with different irrigation and fertilization modes were analyzed. The results show that in surface water, the average concentration of NH₄⁺-N at seven days after the application of basal fertilizer using the reducing fertilization mode was 46.14% of that using the conventional fertilization mode, while the average concentration of NO₃^--N was 83.62% of that using the conventional fertilization mode. The controlled and mid-gathering irrigation mode coupled with reducing fertilization can prolong the field water storage time, allow nitrogen to infiltrate more rapidly and reserve in the tilth layer, and lead to the improvement of effective utilization of nitrogen, the decrease of the nitrogen concentration in surface drainage, and the decrease of nitrogen deep seepage. High nitrogen concentration of surface water was sustained in four days after fertilization. It is pointed out that drainage should be controlled during this period, so that the loss of nitrogen fertilizer can be avoided and the agricultural non-point source pollution caused by nitrogen fertilization can be alleviated.